Field
The present disclosure relates to a liquid crystal display device, and more particularly, to a liquid crystal display device with minimized light leakage that may occur between a liquid crystal display panel and a backlight unit.
Description of the Related Art
A liquid crystal display (LCD) device is a display device for displaying an image by adjusting the transmissivity of light generated from a light source. In the LCD device, the light source is disposed under a liquid crystal and an electric field is applied to the liquid crystal to control alignment of the liquid crystal. The LCD device is applied to various electronic devices such as a smartphone, a tablet PC, etc. Particularly, in recent years, studies for reducing a bezel area of the LCD device are being actively conducted to achieve a beautiful design of the LCD device and reduce a size of the LCD device.
A typical LCD device includes a backlight unit including a light source and a liquid crystal display panel disposed on the backlight unit. The backlight unit and the liquid crystal display panel are bonded to each other by an adhesive tape. However, as a bezel area of the LCD device is reduced, a size of the adhesive tape is also reduced. Therefore, an adhesive area of the adhesive tape may also be reduced. The reduction in adhesive area of the adhesive tape causes various problems such as a decrease in adhesion of the adhesive tape and occurrence of a light leakage from the LCD device.
FIG. 1 is a cross-sectional view provided to explain a cause of occurrence of a light leakage from an LCD device. Referring to FIG. 1, an LCD device 100 includes a liquid crystal display panel 110, a backlight unit 120, a cover glass 150 that covers the liquid crystal display panel 110, a frame 160 surrounding an edge of the cover glass 150, and an adhesive member 165 that bonds the frame 160 to the cover glass 150.
A light generated from a light source in the backlight unit 120 is incident into a lower polarizing plate 111 of the liquid crystal display panel 110 through a light guide plate 121 and an optical sheet 123. The light incident into the lower polarizing plate 111 penetrates a liquid crystal 113 disposed between a lower substrate 112 and an upper substrate 114 of the liquid crystal display panel 110 to be incident into an upper polarizing plate 115 and emitted to an active area A/A of the cover glass 150.
The backlight unit 120 and the liquid crystal display panel 110 are bonded to each other by an adhesive tape 142. In this case, a space is formed between the backlight unit 120 and the liquid crystal display panel 110 due to a thickness of the adhesive tape 142. Most of the light emitted through the optical sheet 123 of the backlight unit 120 is incident into the lower polarizing plate 111 of the liquid crystal display panel 110. However, some of the light may be leaked through the space between the backlight unit 120 and the liquid crystal display panel 110. In this case, the adhesive tape 142 has a light shielding property in order to absorb the leaked light.
However, as the active area A/A is increased and a bezel area B/A is reduced, an area for the adhesive tape 142 may be reduced. Particularly, the adhesive tape 142 has a light shielding property and thus cannot be disposed in the active area A/A but can be disposed only in the bezel area B/A. Therefore, if the bezel area B/A is reduced, a width of the adhesive tape 142 is reduced. However, as the width of the adhesive tape 142 is reduced, an adhesive area of the adhesive tape 142 is reduced. Therefore, adhesion of the adhesive tape 142 may be reduced. If a width of the bezel area B/A is 1 mm or less, adhesion of the adhesive tape 142 is greatly reduced. Therefore, the liquid crystal display panel 110 and the backlight unit 120 may be separated. Thus, a light may be easily leaked through a separated region between the liquid crystal display panel 110 and the backlight unit 120. Further, as the width of the adhesive tape 142 is reduced, a light shielding property of the adhesive tape 142 is also reduced. Therefore, the adhesive tape 142 may not sufficiently suppress a light leakage.
Alight leaked between the liquid crystal display panel 110 and the backlight unit 120 may be emitted to the bezel area B/A of the cover glass 150, and the light can be slightly seen from the outside. Therefore, an additional light shielding film may be attached to a bottom surface of the cover glass 150 in order to suppress occurrence of a light leakage from the bezel area B/A of the cover glass 150. However, even if the light shielding film reduces a light leakage to a certain degree, a light leakage may slightly occur between the cover glass 150 and an outer case of the LCD device 100 in contact with a lateral surface of the cover glass 150. For example, the outer case of the LCD device 100 may be disposed to be in contact with the lateral surface of the cover glass 150 without covering a top surface of the cover glass 150 in order to achieve a beautiful design of the LCD device 100. In this case, a micro space may be formed between the outer case and the lateral surface of the cover glass 150 due to a process error. A light leaked between the liquid crystal display panel 110 and the backlight unit 120 may be seen through the micro space between the cover glass 150 and the outer case.
Further, recently, the outer case of the LCD device 100 has various colors, and the LCD device 100 including a bright color outer case can be manufactured. Particularly, for uniformity in design of the LCD device 100, an edge of the cover glass 150 in the LCD device 100 including a bright color outer case may be formed to have the same bright color as the outer case. Therefore, the light shielding film attached to the bottom surface of the cover glass 150 needs to have a bright color. Further, since the frame 160 disposed under the cover glass 150 can be seen from the outside through the cover glass 150, the frame 160 needs to have a bright color or needs to be transparent. When the light shielding film and the frame 160 have a bright color, the light shielding property is reduced. Therefore, a light leaked between the liquid crystal display panel 110 and the backlight unit 120 may penetrate the frame 160 and the light shielding film each having the reduced light shielding property and may be slightly seen from the outside.
Meanwhile, as the bezel area B/A is reduced, a width of the frame 160 is also reduced. If the width of the frame 160 is reduced, an adhesive area between the frame 160 and the cover glass 150 is also reduced. Therefore, adhesion between the frame 160 and the cover glass 150 may be reduced, and, thus, the frame 160 and the cover glass 150 may be separated. In order to suppress such separation, the adhesive member 165 for reinforcing the adhesion between the frame 160 and the cover glass 150 may be used. The adhesive member 165 may be formed by bonding the cover glass 150 to the liquid crystal display panel 110 and then coating an adhesive on an edge where a lateral surface of the frame 160 is connected to the bottom surface of the cover glass 150. However, as the bezel area B/A is reduced, a physical space to be coated with the adhesive is reduced. Thus, it may be difficult to bond the frame 160 to the cover glass 150 using the adhesive member 165. Further, since the adhesive area of the adhesive member 165 is reduced, the adhesion between the frame 160 and the cover glass 150 may be reduced. Thus, durability of the frame 160 may be reduced and durability of the LCD device 100 may also be reduced.